Abdominal Ultrasound:
Liver

Indications for performing this procedure:  As a diagnostic tool, hepatic ultrasound is very useful in differentiating between diffuse vs. focal lesions of the liver, in detecting post-hepatic bile duct obstruction and choleliths (gall stones), and in facilitating ultrasound-guided fine needle aspirates and core biopsies.

    It is important to note that ultrasound is limited in that it can give information that an anatomic change is present, but may not be able to give definitive diagnostic information as to the etiology of the change.  Diagnosis can only be confirmed with a tissue biopsy.   Furthermore, a normal hepatic ultrasound does not rule out the possibility that diffuse disease is present.

Interpretation of Hepatic Conditions:       The liver can appear either normal, hyperechoic, or hypoechoic with diffuse liver disease, depending on the nature of the pathologic change.   Conditions that cause the liver to appear hyperechoic include fibrosis or hepatic lipidosis.   Condition that cause the liver to appear hypoechoic include suppurative hepatitis or hepatic congestion.  Hepatic lymphosarcoma is variable in sonographic characteristics, and may appear either hyperechoic or hypoechoic.  Left:  This is an example of an ultrasound picture from a normal liver.  Notice that the liver's echogenicity is homogeneous.

• Focal Lesions:  Hepatic ultrasound can detect the presence of focal lesions which could be cysts, hematomas, regenerative nodules, abscesses, granulomas, or neoplasms.  Cysts are generally anechoic, but the remainder of the lesions can have variable echogenicities on ultrasound.  A biopsy is needed for a definitive diagnosis.  Ultrasound is useful when performing a fine needle aspirate from a focal lesion in the liver, as one can visualize the needle as it is directed into the target tissue.

• Biliary Obstruction:  Extrahepatic bile duct obstruction can be reliably detected with ultrasound.  Early in the course of obstruction, the gallbladder appears distended and there is loss of normal tapering between the neck of the gall bladder and cystic duct.   The common bile duct will also appear distended.  If the obstruction has been present for as long as a week, intrahepatic bile ducts will also distend and appear as short, abruptly branching hypoechoic linear structures throughout the liver.

The Gall Bladder:  Ultrasound can reveal changes in the thickness of the gall bladder wall.  A diffusely thickened wall may be due to cholecystitis.  Focal thickenings of the wall could be neoplasia.  Ultrasound can also enable the visualization of choleliths which appear as hyperechoic foci within the gall bladder, casting a hallmark sign of "acoustic shadowing", which indicates complete reflection of sound by the choleliths.

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